In order to maintain a constant color level in the color output of a digital video decoder, automatic color saturation control is required. The goal of this automatic color saturation control is to maintain a constant color level as the strength of the signal varies over time. In general, color saturation control utilizes the amplitude of the color burst as a benchmark wherein the amplitude of the burst is measured and then compared with an ideal value. The ratio of the ideal burst amplitude to the measured burst amplitude is then computed and multiplied by the nominal cb and cr factors to produce multiplication factors, these factors being the color difference signals in a YCrCb color format. These multiplication factors are then applied to the demodulated U and V color difference signals within the video decoder in the YUV color format.
When implementing the above-noted algorithm, a number of divisions and multiplication operations are required to define the ratio. Typically, these division and multiplication operations are implemented by initially looking up an approximate value for the reciprocal of the measured value in a lookup table, and then refining it with the Newton Raphson recursive relation to improve the accuracy. This processing requires not only the use of a lookup table, but also multiplications which consumes a large portion of a simple microprocessor's throughput. The refine process can be eliminated at the expense of a course approximation. The lookup process itself involves a large amount of code which examines the measured burst amplitude and determines a range bin corresponding to an approximation to the ratio. The ratio must then be multiplied times the nominal cr and cb factors.